Re: Audio Glitch in Matlab (Trevor Agus )


Subject: Re: Audio Glitch in Matlab
From:    Trevor Agus  <Trevor.Agus@xxxxxxxx>
Date:    Tue, 18 Oct 2011 13:43:57 +0200
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

Dear list, For the set-ups I've tried, I seem to get truncation clicks for everything on Windows 7 and also the ASIO-based functions on Windows XP. [I wasn't able to compile playrec successfully for Windows 7 and I haven't yet tried SoundMexPro.] If you want to measure exactly how many samples your machine is truncating, you can play a signal that consists entirely of zeros except for a single "1" near the end of the stimulus. If the "1" is presented, you'll hear a reassuring click; if it's truncated; you'll get silence. With ASIO, the amount truncated seems to depend reliably on the number of samples presented. On my set-up, all complete blocks of 256 samples were presented reliably, but the last incomplete block was truncated, i.e., the number of truncated samples were mod(length(wave),256). If I used Matlab's native functions with Windows 7, the amount truncated seemed to have a random factors (and varied with the exact command used), but 40 ms of silence at the end seemed to leave a big enough safety margin for everything. It's not too much hardship to add 40 ms of silence to the end, especially if you build it into a single function that adds the silence then presents the sound. Alternative solutions include sticking with XP or switching to Macs... Trevor


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